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%I #15 Jul 25 2015 15:52:48
%S 1,2,3,10,11,12,13,20,100,101,102,103,110,111,112,1000,1001,1002,1003,
%T 1010,1011,1012,1013,1020,10000,10001,10002,10003,10010,10011,10012,
%U 10013,10020,10100,10101,100000,100001,100002,100003,100010,100011
%N n written in base where place values are positive squares.
%C For n>1: A000196(n) = number of digits of a(n); A190321(n) = number of nonzero digits of a(n); A053610(n) = sum of digits of a(n). [_Reinhard Zumkeller_, May 08 2011]
%H Reinhard Zumkeller, <a href="/A007961/b007961.txt">Table of n, a(n) for n = 1..10000</a>
%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">Only Problems, Not Solutions!</a>.
%p A007961 := proc(n)
%p local k,nrem,L,b,d;
%p k := floor(sqrt(n)) ;
%p nrem := n ;
%p L := [] ;
%p for b from k to 1 by -1 do
%p d := floor(nrem/b^2) ;
%p L := [d,op(L)] ;
%p nrem := nrem -d*b^2 ;
%p end do:
%p add( op(i,L)*10^(i-1),i=1..nops(L)) ;
%p end proc: # _R. J. Mathar_, Jul 25 2015
%o (Haskell)
%o import Data.Char (intToDigit)
%o a007961 :: Integer -> Integer
%o a007961 n = read $ map intToDigit $
%o t n $ reverse $ takeWhile (<= n) $ tail a000290_list where
%o t _ [] = []
%o t m (x:xs)
%o | x > m = 0 : t m xs
%o | otherwise = (fromInteger m') : t r xs
%o where (m',r) = divMod m x
%o -- _Reinhard Zumkeller_, May 08 2011
%Y Cf. A000290, A000433.
%K nonn,base
%O 1,2
%A R. Muller
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